Process for the production of vinyl esters

ABSTRACT

IMPROVEMENT IN A PROCESS FOR THE PRODUCTION OF VINYL ESTERS BY REACTING ETHYLENE, LOWER CARBOXYLIC ACIDS WITH 2 TO 4 CARBON ATOMS AND OXYGEN IN THE GAS PHASE AT ELEVATED TEMPERATURE AND NORMAL OR ELEVATED PRESSURE, IN THE PRESENCE OF SUPPORTED CATALYST CONSISTING ESSENTIALLY OF PALLADIUM, GOLD AND AN ALKALI METAL ACETATE ON A SILICIC ACID SUPPORT, WHICH IMPROVEMENT COMPRISES PREPARING THE CATALYST BY TREATING THE SUPPORT, SIMULTANEOUSLY OR SUCCESSIVELY OR IN COMBINATION WITH A SOLUTION A DND A SOLUTION B, THE SOLUTION A CONTAINING DISSOLVED SALTS OF PALLADIUM AND GOLD AND THE SOLUTION B CONTAINING COMPOUNDS WHICH ARE ABLE TO REACT ON THE CATALYST SUPPORT WITH THE NOBLE METAL SALTS OF THE SOLUTION A TO FORM WATER-IN-SOLUBLE NOBLE METAL COMPOUNDS WHICH ARE SUBSTANTIALLY FREE OF HALOGEN, SULPHUR AND NITROGEN, IMPREGNATING THE CATALYST SUPPORT WITH THE SOLUTIONS A AND B IR WITH THE COMBINED SOLUTION OF A AND B IN QUANITIES WHICH CORRESPOND TO FROM 1 TO 110% OF THE ABSORPTIVE CAPACITY OF THE CATALYST SUPPORT FOR THESE SOLUTIONS: SUBJECTING THE CATALYST SUPPORT IMPREGNATED WITH THE SOLUTIONS A AND B TO A TIME/ TEMPERATURE-TREATMENT WHICH IS SUCH THAT 95% AT LEAST OF THE IMTHE IMPREGNATED PALLADIUM AND 95% AT LEAST OF THE IMPREGNATED GOLD IS TRANSFORMED INTO WATER-INSOLUBLE NOBLE METAL COMPOUNDS, TREATING THE WATER-INSOLUBLE NOBLE COMPOUNDS WITH A REDUCING AGENT TO COVEY THESE COMPOUNDS SUBSTANTIALLY INTO THE CORRESPONDING NOBLE METALS AND REMOVING THE WATER-SOLUBLE COMPOUNDS WHICH ARE CONTAINED IN THE CATALYST BY WASHING, AND APPLYING AN ALKALI METAL COMPOUND BEFORE OR AFTER THE TREATMENT WITH THE REDUCIING AGENTS, THE ALKALI METAL COMPOUNDS CONSISTING OF ALKALI METAL CARBOXYLATES OR OF ALKALI METAL COMPOUNDS WHICH ARE WHOLLY OR IN PART TRANSFORMED INTO ALKALI METAL CARBOXYLATES UNDER THE REACTION CONDITIONS.

United States Patent 3,822,308 PROCESS FOR THE PRODUCTION OF VINYLESTERS Walter Kronig and Gerhard Scharfe, Leverkusen, Germany, assignorsto Bayer Aktiengesellschaft, Leverkuseu, Germany No Drawing.Continuation of application Ser. No.

795,027, Jan. 29, 1969. This application Mar. 13, 1972, Ser. No. 234,322

Int. Cl. C07c 67/04 US. Cl. 260-497 A 14 Claims ABSTRACT OF THEDISCLOSURE Improvement in a process for the production of vinyl estersby reacting ethylene, lower carboxylic acids with 2 to 4 carbon atomsand oxygen in the gas phase at elevated temperature and normal orelevated pressure, in the presence of supported catalyst consistingessentially of palladium, gold and an alkali metal acetate on a silicicacid support, which improvement comprises preparing the catalyst bytreating the support, simultaneously or successively or in combinationwith a solution A and a solution B, the solution A containing dissolvedsalts of palladium and gold and the solution B containing compoundswhich are able to react on the catalyst support with the noble metalsalts of the solution A to form water-in-soluble noble metal compoundswhich are substantially free of halogen, sulphur and nitrogen;impregnating the catalyst support with the solutions A and B or with thecombined solution of A and B in quantities which correspond to from 1 to110% of the absorptive capacity of the catalyst support for thesesolutions: subjecting the catalyst support impregnated with thesolutions A and B to a time/ temperature-treatment which is such that95% at least of the impregnated palladium and 95 at least of theimpregnated gold is transformed into water-insoluble noble metalcompounds, treating the water-insoluble noble metal compounds with areducing agent to convey those compounds substantially into thecorresponding noble metals and removing the water-soluble compoundswhich are contained in the catalyst by washing; and applying an alkalimetal compound before or after the treatment with the reducing agents,the alkali metal compounds consisting of alkali metal carboxylates or ofalkali metal compounds which are wholly or in part transformed intoalkali metal carboxylates under the reaction conditions.

This is a continuation of application Ser. No. 795,027 filed Jan. 29,1969.

This invention relates to a process for the production of vinyl esters.

It is known to prodice vinyl esters by reacting ethylene, certaincarboxylic acids and molecular oxygen or air in the gas phase attemperatures of from 100 to 250 C. and at normal or elevated pressure inthe presence of supported catalysts which contain palladium. Such aprocess has been described, for example, in German Patent SpecificationNos. 1,185,604 and 1,196,644, German Auslegeschrift No. 1,244,766, andBelgian Patent Specification Nos. 671,895 and 671,896.

We have now found that particularly active supported catalystscontaining palladium and gOld for the production of vinyl esters fromethylene, lower carboxylic acids with 2 to 4 carbon atoms and oxygen inthe gas phase at ele vated temperature and at normal or elevatedpressure are obtained by the following process. The catalyst support istreated simultaneously or successively, with or without intermediatedrying, with a solution A and a solution B, the solution A containingdissolved salts of palladium and gold and optionally salts of othermetals, and the solution 3,822,308 Patented July 2, 1974 ice Bcontaining compounds which are able to react on the catalyst supportwith the noble metal salts of the solution A to form water-insolublenoble metal compounds which are practically free from halogen, sulphurand nitrogen; the solution A or B or the common solution of A and B isimpregnated on the catalyst support in quantities which correspond tofrom 10 to 110% of the absorptive capacity of the catalyst support forthese solutions; the catalyst support with the impregnated solutions Aand B is subjected to a time/ temperature treatment which is such thatat least of the impregnated palladium and 95 at least of the impregnatedgold are transformed into waterinsoluble noble metal compounds; thewater-insoluble noble metal compounds are largely transformed by atreatment with reducing agents into the noble metals and thewater-soluble compounds which are contained in the catalyst are removedby washing, before or after the reduction.

In a preferred embodiment of the process, alkali metal carboxylates,especially alkali metal acetates, are applied on the catalyst before orafter the treatment with reducing agents, in such quantities that thecatalyst, after being dried, contains from 1 to 30% by weight of alkalimetal carboxylate. Examples of the alkali metal carboxylates includesodium formate potassium acetate, sodium acetate, lithium acetate,potassium propionate and potassium butyrate.

The following detailed explanations are given for carrying out in such away that, for example, firstly the catalyst support is impregnated withthe solution A, which is then optionally dried, and then it isimpregnated with the solution B. However, it is also possible firstly toimpregnate the support with the solution B, optionally followed bydrying, and then to impregnate it 'with the solution A. Furthermore, thesolution A and B can be mixed and the support may be impregnated withthe common solution.

The solution A or the solution B or the common solution of A and B isused in quantities which correspond from 10 to 110%, advantageously90-100%, of the absorptive capacity of the catalyst support. It ispreferred to use water as a solvent for the solution A and B, but

it is also possible to employ suitable organic or aqueousorganicsolvents.

For example, palladium chloride, sodium-palladium chloride, palladiumnitrate and palladium sulphate can serve as palladium salts in solutionA, and, for example, auric chloride and tetrachloroauric acid can beemployed as gold salts in the solution. In the process according to theinvention, it is advantageous to use the generally accessibletetrachloroauric acid and sodium-palladium chloride, which have goodwater-solubility. The solution A can optionally also contain salts ofother metals, for example of magnesium, calcium, barium, rare earths,chromium molybdenum, tungsten, manganese, rhenium, iron, cobalt, nickel,ruthenium, rhodium, iridium, platinum and copper.

The compounds in solution B can, for example, consist of alkali metalhydroxides, alkali metal bicarbonates and alkali metal carbonates, andthese can be used by themelves of as a mixture.

Substances which, under the reaction conditions, do not lose theirmechanical strength under the influence of acetic acid are particularlysuitable as catalyst supports. Silicic acid and silicates are, forexample, suitable. The catalyst supports can vary within wide limits asregards their physcal properties.

Physical properties in the following range are, for example, suitable:absorptive capacity from -1000 g. of water per'kg. of catalyst support,internal surface accord ing to BET of 50200 m. g. and a mean porediameter of from 100 to 500 A.

The reaction of the compounds of solution B with the noble metal saltsof solution A can, for example, be described by the stoichiometricequations:

The following explanations are also given concerning the processaccording to the invention: the quantities of the compounds contained inthe solution B are preferably such that they are at least sufiicient forthe stoichiometric reaction with the salts contained in the solution Ato form water-insoluble noble metal compounds. However, the compounds inthe solution B can also be employed in excess, for example in 1-10 timesthe quantity which is stoichiometrically necessary. The reaction of thecompounds in the solution B with the noble metal salts of the solution Ato form insoluble noble metal compounds takes place on the support,either quickly or slowly, according to the conditions which are used.Other compounds which influence the speed of the reaction can be addedto the solution B, e.g. salts of weak acids and strong bases or salts ofstrong acids and weak bases, for example, sodium acetate or sodiumphosphates. If the solutions A and B are mixed before being used forimpregnation, there is generally a precipitation of water-insolublenoble metal compounds after a certain time. In this case, theimpregnation with the common solution is preferably effected before theprecipitation of the water-insoluble noble metal compounds. The reactionof the compounds of solution B with the noble metal salts of solution Aon the support is generally completed after about 24 hours. Then 95% atleast of the palladium and 95% at least of the gold are converted intowater-insoluble noble metal compounds.

In carrying out the process according to the invention, the reaction ofthe solutions on the support can be performed at normal or elevatedtemperature, for example 70 A. After the reaction is complete, thewater-soluble compounds which are contained in the catalyst support,e.g. alkali metal chlorides and also any excess of the compoundscontained in solution B which may be present, are removed by washingwith water. The catalyst washed with water is treated with alkali metalcarboxylate solutions, so that the catalyst, after drying, contains from1 to 30% by weight of alkali metal carboxylate. The water-washedcatalyst can be dried before the treatment with alkali metalcarboxylates, whereupon the latter can be applied for impregnationpurposes as a solution.

The alkali metal carboxylates can also be applied by introducingsolutions containing alkali metal carboxylates into the hot gas streambefore the reactor, and then vaporizing the solutions together with thealkali metal carboxylates, so that the alkali metal carboxylates aresupplied in gaseous form to the catalyst.

The water-insoluble noble metal compounds contained in the catalystafter the time/temperature treatment are treated with reducing agents.This can take place before or after the washing to remove thewater-soluble compounds and before or after the application of thealkali metal compounds.

The reduction can be effected in liquid phase, e.g. with aqueoushydrazine hydrate, or in the gas phase, e.g. with hydrogen, ethylene ormethanol vapours. The reduction can be carried out under normal orelevated temperature, and at normal or elevated pressure. Preferredprocedures as regards the reduction according to the invention are thetreatment of the water-washed catalyst with ethylene at 100-200" C. andpressures of from 1-10 atm. gauge, or the treatment of the catalystwhich has not been washed with water and prior to the washing withaqueous or aqueous alkaline hydrazine solutions at normal pressure andat room temperature. The prepared catalyst advantageously contains from0.5 to 6.0 g. of palladium and from 0.1 to 3.0 g. of gold per litre ofthe catalyst (bulk volume).

Instead of applying alkali metal carboxylates to the catalyst, it isalso possible to start with alkali metal compounds which are transformedwholly or in part into alkali metal carboxylates under the reactionconditions, such as alkali metal hydroxides, carbonates, borates andphosphates. Lower carboxylic acids with 2-4 carbon atoms include aceticacid, propionic acid, isobutyric acid and n-butyric acid.

The invention is illustrated by the following examples.

EXAMPLE 1 The catalyst was prepared in the following manner: 1 litre ofa silicic acid support with an internal surface area of m. /g., a weightper unit volume of 0.5 g./cc. and an absorptive capacity of 400 ml. ofwater per litre of catalyst support was evacuated in a shaker-typevessel and then impregnated, while shaking, with 390 ml. of an aqueoussolution of Na PdCl and HAuCl which corresponded to a quantity of 3.3 g.of Pd and 1.5 g. of Au. The catalyst was thereafter dried in a rotaryevaporator under a water jet vacuum. The dried catalyst was evacuated ina shaker-type vessel and treated while shaking with a solution of 6 g.of NaOH in 390 ml. of water. The catalyst was left to stand for 16 hourswith distilled water. By analysing the washing water, it was found thatmore than 99% of the palladium introduced and more than 98% of the goldhad been converted into water-insoluble compounds. The catalyst wasdried, whereupon it was impregnated with 30 g. of potassium acetate asan aqueous solution, and the catalyst was dried again. Finally, thecatalyst was reduced at C. and at 5 atm. gauge for 24 hours in a streamof ethylene. 2,330 mi. of the catalyst thus prepared were introducedinto a reaction tube having a length of 5 m. and an internal diameter of25 mm. 51.7 mols of acetic acid, 169.5 mols of ethylene and 16.6 mols ofoxygen per hour in gaseous form were then conducted at the inlet of thereactor over the catalyst at 176 C. and a pressure of 5.3 atm. gauge.452 g. of vinyl acetate were formed hourly per litre of catalyst. Of theethylene reacted, 91.6% had been converted into vinyl acetate and 8.4%into carbon dioxide.

EXAMPLE 2 The catalyst was prepared in the following manner: 1 litre ofthe catalyst support of Example 1 was impregnated with 400 ml. of anaqueous solution containing 12 g. of NaOH and dried, whereupon it wasimpregnated with 380 ml. of an aqueous solution of Na PdCl and HAuClwhich corresponds to an amount of 3.3 g. of Pd and 1.5 g. of Au. Thecatalyst was left standing for 24 hours at room temperature. Washing ofthe catalyst, impregnation with alkali metal acetate and reduction withethylene were carried out in the same manner as in Example 1. Under thesame reaction conditions as in Example 1, results were obtained with thecatalyst which are comparable with those of Example 1.

EXAMPLE 3 The catalyst was prepared in the following manner: An aqueoussolution of Na PdCl and HAuCl was added while stirring to a solution of42 g. of K 00 in water. The combined solution was diluted with water to390 ml. and 1 litre of the catalyst support referred to in Example 1 wasimpregnated therewith. The catalyst was left standing for 16 hours atroom temperature. Washing of the catalyst, impregnation with alkalimetal acetate and reduction with ethylene took place in the same way asin Example 1. Under the same reaction conditions as in Example 1,results were obtained with the catalyst which are comparable with thoseof Example 1.

EXAMPLE 4 The catalyst was prepared as in Example 1, but a support wasused which had an internal surface of m. /g.; before the catalyst wasimpregnated with potassium acetate, it ws reduced for 4 hours withethylene at 150 C., without using pressure. 2,330 ml. of the catalystthus prepared were placed in a. reaction-tube with a length of 5 m. andan internal diameter of 25 mm. 200 mols of ethylene, 60 mols of aceticacid and 15 mols of oxygen per, hour were conducted in gaseous form overthe catalyst, with a pressure of 8.2 atm. gauge at the inlet to thereactor. The gas was heated before entering the reactor in a superheaterto the reaction temperature. A solution of potassium acetate in aceticacid was continuously pumped into the reactor and vaporised. .p.p.m. ofpotassium as potassium acetate based on the amount of acetic acidintroduced at the inlet of the reactor were continuously supplied to thereactor. The test was carried out over a period of 2,100 hours. Duringthis time, the reaction temperature was raised from 156 to 168 C. Onaverage, throughout the entire test, 380 g. of vinyl acetate were formedper litre of catalyst and per hour. of the reacted ethylene, 96% wasconverted to vinyl acetate and 4% to carbon dioxide.

EXAMPLE 5 The catalyst was prepared as in Example 4, but, beforeimpregnating the catalyst with potassium acetate, it was reduced with anaqueous hydrazine solution, washed with water and dried.

900 ml. of catalyst thus obtained were introduced into a reaction tubewith a length of 2 In. and an internal diameter of 25 mm. 77 mols ofethylene, 19 mols of acetic acid and 5.8 mols of oxygen per hour wereconducted in gaseous form over the catalyst at 140 C. and at a pressureof 8 atm. gauge. 235 g. of vinyl acetate were formed per litre ofcatalyst and per hour. Of the reacted ethylene, 97.7% was converted tovinyl acetate and 2.3% to carbon dioxide.

EXAMPLE 6 The catalyst was prepared in the following manner: 1 litre ofa silicic acid support with an internal surface of 165 m. /g., a weightper unit volume of 0.5 g./cc. and an absorptive capacity of 400 ml. ofWater per litre of catalyst support was evacuated in a shaker-typevessel and then impregnated, while shaking, with 390 ml. of an aqueoussolution of Na PdC1 and HAuCl which corresponded to a quantity of 3.3 g.of Pd and 1.5 g. of Au. The catalyst was thereafter dried in a rotaryevaporator under a water jet vacuum. The dried catalyst was left tostand for 16 hours at room temperature and was then washed for 24 hourswith distilled water. By analysing the washing water, it was found thatmore than 99% of the palladium introduced and more than 98% of the goldintroduced has been converted into water-insoluble compounds. Thecatalyst was then dried, whereupon it was impregnated with 30 g. ofpotassium acetate as an aqueous solution, and was then dried again.Finally, the catalyst was reduced at 150 C. and at 5 atm. gauge for 24hours in a stream of ethylene. 900 ml. of catalyst thus prepared wereintroduced into a reaction tube having a length of 2 m. and an internaldiameter of 24 mm. 6.3 mols of propionic acid, 84 mols of ethylene and6.2 mols of oxygen per hour in gaseous form were then conducted over thecatalyst at 140 C. and an inlet-pressure of 8 atm. gauge, 289 g. ofvinyl acetate were formed every hour per litre of catalyst. Of theethylene reacted, 96% had been converted into vinyl acetate and 4% intocarbon dioxide.

EXAMPLE 7 The catalyst was prepared as in Example 6, but using a silicicacid support with an internal surface of 130 mF/g. and treating thecatalyst, after the treatment with the sodium hydroxide solution, withan aqueous hydrazine solution at room temperature. The catalyst wasthereafter washed with water, dried and then coated with potassiumacetate, as in Example 6. 900 ml. of the catalyst thus obtained wereintroduced into a reaction tube with a length of 2 m. and an internaldiameter of 25 mm. 6.3 mol of isobutyric acid, 84 mols of ethylene and6.2 mols of oxygen were hourly conducted in gaseous form over thecatalyst at C. and at a pressure of 5 atm. gauge. g. of vinylisobutyrate were formed per litre of catalyst per hour. Of the reactedethylene, 96% was converted to vinyl isobutyrate and 4% to carbondioxode.

What we claim is:

1. Improvement in a process for the production of vinyl esters byreacting ethylene, lower carboxylic acids with 2 to 4 carbon atoms andoxygen in the gas phase at elevated temperature and normal or elevatedpressure, in the pres ence of supported catalyst consisting essentiallyof palladium, gold and an alkali metal acetate on a silicic acidsupport, which improvement comprises preparing the catalyst by treatingthe support, simultaneously or succesively or in combination with asolution A and a solution B, the solution A containing dissolved saltsof palladium and gold and the solution B containing compounds which areable to react on the catalyst support with the noble metal salts of thesolution A to form water-in-soluble noble metal compounds which aresubstantially free of halogen, sulphur and nitrogen; impregnating thecatalyst support with the solutions A and B or with the combinedsolution of A and B in quantities which correspond to from 1 to 110% ofthe absorptive capacity of the catalyst support for these solutions:subjecting the catalyst support impregnated with the solutions A and Bto a time/temperature-treatment which is such that 95% at least of theimpregnated palladium and 95% at least of the impregnated gold istransformed into water-insoluble noble metal compounds, treating thewater-insoluble noble metal compounds with a reducing agent to conveythose compounds substantially into the corresponding noble metals andremoving the water-soluble compounds which are contained in the catalystby washing; and applying an alkali metal compound before or after thetreatment with the reducing agents, the alkali metal compoundsconsisting of alkali metal carboxylates or of alkali metal compoundswhich are wholly or in part transformed into alkali metal carboxylatesunder the reaction conditions.

2. A process according to claim 17, in which said alkali metal compoundis an alkali metal carboxylate.

3. A process according to claim 2, in which the alkali metal compoundsare applied in such quantities that the catalyst, after being dried,contains from 1 to 30% by weight of alkali metal carboxylate.

4. A process according to claim 1, in which water is used as a solventfor solution A and solution B or for the combined solution A and B.

5. A process according to claim 1, in which sodiumpalladium chloride (NaPdCl and tetrachloroauric acid (HAuCl ar used as noble metal salts.

6. A process according to claim 4, in which water is used as a solventfor solution A and solution B or for the combined solution A and B.

7. A process according to claim 1, in which alkali metal hydroxides,alkali metal bicarbonates or alkali metal carbonates separately or inadmixture, are contained in solution B as compounds which react on thecatalyst support with the noble metal salts, with the formation ofwaterinsoluble noble metal compounds which are substantially free ofhalogen, sulphur and nitrogen.

8. A process according to claim 5, in which sodium-palladium chloride(Na PdCl and tetrachloroauric acid (HAuCl are used as noble metal salts.

9. A process according to claim 1, wherein impregnation is firstlyeffected with the solution A, followed by drying, and then with solutionB.

10. A process according to claim 1, wherein the solution A and thesolution B are used for impregnation on the catalyst in quantities whichcorrespond to 90-100% of the absorptive capacity of the catalyst forthese solutions.

11. A process according to claim 9, wherein impregnation is firstlyeffected with the solution A, followed by drying, and then with solutionB.

12. A process according to claim 1, wherein the noble metal salts areused in such quantities that the prepared catalyst contains from 0.5 to6.0 g. of palladium and from 0.1 to 3.0 g. of gold per liter ofcatalyst.

13. A process according to claim 10, wherein the solution A and thesolution B are used for impregnation on the catalyst in quantities whichcorrespond to 90-100% of the absorptive capacity of the catalyst forthese solutions.

14. A process according to claim 1, wherein the silicic 8 ReferencesCited UNITED STATES PATENTS 3,579,569 5/1971 Montgomery etal. 260-497 A3,488,295 1/1970 Sennewald et al. 260497 A 3,670,014 6/1972 Fernholz260-497 A FOREIGN PATENTS 1,128,993 10/ 1968 United Kingdom 260-497 Aacid support has an internal surface area of from Soto 200 0 LORRAINEWEINBERGER, Primary Examiner mP/g. BET.

R. D. KELLY, Assitant Examiner @353? UNmm s'rA'rlcs lA'lliN'l OFFICE.CER'l'lFlQATE OF COQR'EC'HON Patent No. -1 22,5303 Dated July 2 1974Inventor(s)Walter Kronig and Gerhard Scharfe It is certified that errorappears in the above-identified patent and that said Letters Patent arehereby corrected as shown below:

F In the heading, please insert the following:

claims'priority of German. Serial No. P 16 68 088.9, filed February 1,1968, amended September 28, 1969 and GermanSerial No. P 17 93 519.2,filed September 28, 1969., r r

Column 2 line 61 change the word "of" Column 4, line 75, the w rd I I nn should read 1 --.-was-- Column 6, line 51, the word "ar" should read"are".

Signed and sealed -this 29th day of October 1974.

(SEAL) l Attest: I McCOY M. GIBSON JR. 0. MARSHALL DANN AttestingOfficer Commissioner of Patents

